From rice fields to fresh air: Transforming agricultural waste into a shield against indoor pollution

Researchers in Vietnam develop a sustainable biochar "sponge" that doubles the efficiency of removing toxic formaldehyde from the air

2026-02-06

(Press-News.org) Formaldehyde is a common but unwelcome guest in many modern homes, leaking silently from furniture, flooring, and household products. While this colorless gas is a known respiratory irritant, cleaning it out of the air usually requires expensive or energy-heavy technology. Now, a research team from Vietnam National University has found a clever way to turn agricultural waste into a high-tech filter that breathes new life into indoor spaces.

In a study published in Carbon Research, the team describes how they successfully transformed rice husk ash—a byproduct of rice production—into a specialized "activated biochar." By modifying this charred material with a polymer called polyethyleneimine (PEI), they created a powerful adsorbent specifically designed to hunt down and trap formaldehyde molecules. The research was led by corresponding authors Bang Tam Thi Dao and Chi-Nhan Ha-Thuc from the Faculty of Materials Science and Technology at the University of Science, Vietnam National University. Their approach not only tackles air pollution but also offers a brilliant second life for the massive amounts of rice husk waste generated in Southeast Asia.

"We wanted to create a solution that was as sustainable as it was effective," say the lead researchers. "By using rice husk ash and a low-energy ultrasonic treatment, we avoided the high-temperature calcination usually required in manufacturing. The result is a material that is cheaper to make and much kinder to the environment."

Science Behind the Sponge:

The PEI Advantage: By adding PEI to the biochar, the researchers increased the density of amine functional groups on its surface. These chemical "hooks" are perfect for grabbing formaldehyde, effectively doubling the material's adsorption capacity compared to standard biochar. Smart Manufacturing: The team used a combination of chemical activation and ultrasonic treatment. This skip the traditional high-heat steps, significantly reducing the carbon footprint of producing the filter material itself. Precision Characterization: Using advanced tools like scanning electron microscopy (SEM) and infrared spectroscopy (FT-IR), the team proved that the PEI-modified biochar has a unique porous structure that acts like a microscopic labyrinth, trapping pollutants deep within. Proven Performance: Kinetic and isotherm studies confirmed that the adsorption process is highly stable and follows predictable scientific models, making it a reliable candidate for commercial air purifiers. This breakthrough from Vietnam National University highlights the growing importance of "circular chemistry"—where the waste from one industry (agriculture) becomes the raw material for another (environmental protection). As urban populations spend more time indoors, the work of Bang Tam Thi Dao and Chi-Nhan Ha-Thuc provides a scalable, cost-effective way to ensure the air we breathe at home is safe. By turning local agricultural remnants into high-value environmental tools, these Vietnamese scientists are proving that the keys to a cleaner future might already be sitting in our fields.

Corresponding Authors:

Bang Tam Thi Dao

Faculty of Materials Science and Technology, University of Science, Ho Chi Minh City, Vietnam. Vietnam National University, Ho Chi Minh City, Vietnam.

Chi-Nhan Ha-Thuc

Faculty of Materials Science and Technology, University of Science, Ho Chi Minh City, Vietnam. Vietnam National University, Ho Chi Minh City, Vietnam.

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Journal reference: Huynh, T.L., Dao, B.T.T., Le, M.T. et al. Polyethyleneimine-modified activated biochar derived from rice husk ash: material development and preliminary formaldehyde adsorption study. Carbon Res. 5, 5 (2026).

https://doi.org/10.1007/s44246-025-00244-2

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About Carbon Research

The journal Carbon Research is an international multidisciplinary platform for communicating advances in fundamental and applied research on natural and engineered carbonaceous materials that are associated with ecological and environmental functions, energy generation, and global change. It is a fully Open Access (OA) journal and the Article Publishing Charges (APC) are waived until Dec 31, 2025. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon functions around the world to deliver findings from this rapidly expanding field of science. The journal is currently indexed by Scopus and Ei Compendex, and as of June 2025, the dynamic CiteScore value is 15.4.

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